Stability and reliability of multiplexer products
One.
Features of FM multiplexer(Our FM multiplexer series products have the following characteristics.)
1.Various structural forms.
The basic structural units of FM multiplexers produced by our company include various structural forms, such as bridge type (constant impedance type), star type (star point type), delay type (phase sensitive type), improved bridge type, and hybrid structure composed of various basic units. At present, the design of FM multiplexer has been fully modularized. We can customize FM multiplexer products for users according to their different needs.
2.
Multiple power levels. Our company provides users with multiple power levels of FM duplexer units, including 1kW, 2kW, 3kW, 5kW, 10kW, 20kW, etc. The application of these unit modules can easily form various FM duplexers required by users.
3.
All indicators are excellent. Our company uses high-quality raw materials and advanced processing technology to produce FM multiplexers with excellent technical indicators. For example, the central frequency insertion loss of the FM duplexer FSCC200 applied to the 10kW power level is less than 0.15dB.
4.
The frequency is adjustable in full frequency band. At present, the working frequency of all FM multiplexers designed and produced by our company is adjustable in the full frequency band of 87~108MHz. If the user needs to change the frequency of the multiplexer, our engineers can complete the frequency change within 30 minutes without replacing any parts of the multiplexer after arriving at the user's site.
5.
Meet CDR standards. The FM multiplexers produced by our company have been optimized and designed. Except for some special products, the standard multiplexer products meet the requirements of the CDR standard and can realize the synthesis of CDR channels.
6.
The best synthesis scheme. Our company designs the optimal multiplexer synthesis scheme for users according to their different frequency and power requirements, taking into account their special requirements for multiplexer volume, scalability, project budget and other factors. The filters in the FM multiplexer include three cavity, three cavity band cross coupling, four cavity band cross coupling and other different structures, which can achieve channel synthesis with a minimum frequency interval of 0.4 MHz.
7.
Compact structure design. The structure of FM multiplexers produced by our company has been carefully designed and optimized to ensure the rationality of product layout, improve the space utilization rate as much as possible, and reduce the floor area and product weight.
8.
Special specification customization. According to the different needs of users, our company makes scientific analysis and fine design to tailor the FM multiplexer to meet the special needs of users.
Two.
Stability and reliability of FM multiplexer(For the following reasons, our FM multiplexer products have first-class stability and reliability.)
1.
Our company has strong R&D strength to ensure that multiplexer products have excellent stability and reliability at the beginning of design. All multiplexer products of the company, as well as various component-level products (such as filters, couplers, dummy loads, connecting accessories, etc.) that constitute multiplexers, must go through a strict computer simulation stage. On the premise of ensuring that the technical indicators of various products meet the design requirements, engineers will also focus on the distribution of electric and magnetic fields and heat dissipation of various products. We will accurately analyze the distribution of electric field and magnetic field in the product, find out the position where the electric field is the strongest and the most likely to occur, and make targeted modifications to the product structure, so that the product can achieve the maximum power capacity and improve the reliability of the product on the premise of ensuring excellent technical indicators. At the same time, the company's engineers will also simulate the heat dissipation of the product at work, the purpose of which is also to find the weak link in the heat dissipation of the product during the design process and focus on improving it. The following are the computer simulation results of some FM filters and 3dB couplers completed by our company. FM filters and 3dB couplers are the core components of FM multiplexers.
Computer Simulation Results of Electric Field Distribution of 10kW FM Bandpass Filter
Computer simulation results of heat dissipation of 10kW FM bandpass filter
Computer Simulation Results of Electric Field Distribution of 50kW FM 3dB Coupler
2.
Experience and concept advantages. Our core team has nearly 20 years of experience in the development and production of radio and television passive equipment, and has produced more than 2000 sets of FM and TV multiplexers. The sales of multiplexer products cover all provinces, autonomous regions and municipalities directly under the Central Government except Taiwan, and are exported to more than ten countries. The company's team has accumulated rich experience in many years of practical work, which makes the team and the whole company understand the importance of stable and reliable radio and television transmission products. Therefore, the company guarantees at least 100% power capacity redundancy when designing products. For example, the narrowband power capacity of the FM duplexer unit adopted by our company for the 5kW power level FM duplexer in this project is 10kW, that is, the power capacity redundancy reaches 100%. In addition, when the altitude of the station where the multiplexer product is used increases, the company will also design the multiplexer specifically to further increase the power capacity of the product, so as to offset the negative impact of high altitude on the power capacity of the product and improve the stability and reliability of the multiplexer product. After theoretical analysis and practical application verification, our FM and TV multiplexer products can be used normally at stations with an altitude of 3500 meters.
3.Technological advantages. The company has a variety of processing processes and methods to ensure that the products have ideal stability and reliability at the production stage. First of all, the company strictly controls the raw materials, and only selects the metal materials and insulating media materials from regular manufacturers with test reports. Secondly, the company strictly controls the special process steps (such as welding, electroplating, etc.) that have an important impact on the stability and reliability of the product, and uses various technical means and equipment to strictly inspect the results of the special process steps to ensure that every ex-factory product is qualified. Thirdly, the company has selected excellent domestic aluminum profile manufacturers to process aluminum profiles for us, which are used to produce external cavities of FM filters and couplers. Using high-quality aluminum profiles to process the cavity, on the one hand, can effectively reduce the processing cost of the product; More importantly, the consistency index of the cavity processed with aluminum profiles is greatly improved compared with the cavity assembled or welded by plates, which can ensure that the technical index of the mass production product is very close to the prototype, and further improve the stability and reliability of the product.
4.
Engineering advantages. Our company has rich experience in the construction of radio and television multiplexer projects to ensure that the stability and reliability of the products are maximized. First of all, all technical personnel in charge of engineering projects of the company must undergo strict training and assessment of the company before they can complete the multiplexer engineering installation project. Secondly, the company requires the technical personnel to carry out the project construction in strict accordance with the standard process of the Work Specification for Engineering Personnel of Nanjing Zhongru Radio and Television Equipment Co., Ltd. to ensure the stability and reliability of the project construction quality. Thirdly, the connection accessories provided by our company for FM multiplexer products are all high-quality products, including hard feed, elbow, connection assembly, transition, etc. The technical indicators of these connection accessories are excellent, and the consistency of indicators is high, so as to ensure that the indicators of FM multiplexer after system installation will not be inferior to the factory test indicators. Finally, our company has specially developed a software platform for the design of radio and television transmitter room. Before the implementation of various multiplexer construction projects, the company's technology department will conduct a field survey of the construction machine room to obtain accurate data. The technicians will draw the three-dimensional graphics of the entire machine room, including the size of the machine room, the size and location of each equipment, the direction and connection mode of the hard feed between the multiplexer and the transmitter and the antenna feeder, wait. The company will fully communicate with the multiplexer purchaser on the design of the machine room. After the design scheme of the standby room is determined, the project construction will be carried out in strict accordance with the scheme to ensure the project quality and the stability and reliability of the system. Some design legends of the software platform for the radio and television transmitter room design of our company are shown below.
Three.
Experience description of multiplexer commissioning
Our company was founded in 2012, but its core team members have more than 20 years of experience in the research and development, design, production, commissioning and installation of multiplexers. At present, more than 2000 sets of radio and television multiplexers have been working normally in the world with our hands. Our technicians have rich experience in multiplexer commissioning and engineering construction, and can solve various technical problems of multiplexer commissioning and on-site installation, Including system connection and system joint commissioning with multiplexer products from other manufacturers. The recent performance of FM multiplexer projects of our company's technology and some FM multiplexer cases completed by the company's core team members are shown below.
Four.Temperature compensation measures for multiplexer
The temperature stability represents the change degree of the technical index of the multiplexer when the ambient temperature changes, and its unit is kHz/ºC. That is to say, when the ambient temperature of the multiplexer changes by 1 ºC, its operating frequency will change by an offset. The temperature drift of the multiplexer is mainly caused by the frequency drift of the bandpass filter that constitutes the multiplexer.
The bandpass filter is mainly made of metal, including aluminum alloy, copper, brass, etc. When the ambient temperature changes, the size of each component of the filter will produce extremely small deformation due to thermal expansion and contraction. This kind of deformation can't be distinguished by the naked eye, but in the radio and television frequency band, due to the high working frequency of the multiplexer, the very small deformation will also cause relatively obvious change or drift of the working frequency. Generally, if the multiplexer does not design an effective temperature compensation scheme, the temperature coefficient of the multiplexer will reach 10~20kHz/ºC. When the ambient temperature of the filter changes by 25 ºC, the working frequency of the multiplexer will shift by 250~500kHz, which will directly affect the normal operation of the multiplexer, and in serious cases will lead to the paralysis of the entire transmission system. Generally, the temperature coefficient of multiplexer is required to be less than 2kHz/ºC. This requires that the multiplexer must design an effective temperature compensation device to reduce its temperature coefficient.
The filters in the FM multiplexer are all coaxial cavity structures. The main reason for the temperature drift is the change of the length of the conductor inside the filter and the change of the shape of the conductor cavity outside the filter. By solving these two deformation problems, the temperature coefficient of the multiplexer can be reduced to the specified range.
Indium steel is a kind of special alloy steel. Its main characteristic is that it has extremely low coefficient of thermal expansion. The thermal expansion coefficient of this material can be one tenth of that of copper, or even lower. The problem of temperature drift of FM multiplexer can be solved by applying indium steel material to the design of FM filter and FM multiplexer.
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